1. Field of the Invention
This invention relates to optical communications and, more particularly, to a system and method of optical modulation for communication with phased array ultrasonic probes.
2. Description of the Related Art
Ultrasonic imaging systems, as commonly used for medical imaging, require an array of ultrasonic transducers contained within a probe to provide steering and focusing of the ultrasonic beam. Each transducer receives a high frequency signal from the object examined that must then be transmitted back to the host electronic system or imaging console for signal processing. Even with advanced Very Large Scale Integration (VLSI) microelectronic techniques, only a relatively small part of the overall system electronic signal processing may reside at the probe head.
Transmitting the signal requires that the number of cables carrying individual signals back to the host electronics be of the same order as the number of individual transducer elements in the sensing array. Since this number may be greater than 500 in presently envisioned two dimensional arrays, the number of cables required is quite large.
Signals representing the response of individual ultrasonic transducers may be transmitted to the host electronics system from the probe through optical fibers. These fibers are individually small in diameter and may be formed into bundles that are composed of a large number of individual fibers while still maintaining their overall flexibility. While converting the signals to light so that optical fibers may be used improves the flexibility of the bundle, power requirements are increased. Further, combining signals by preprocessing or by multiplexing is limited by the power requirements of these operations and by the power limitations of the probe head. Another obstacle to implementing an optical communications system for ultrasonic probes is the requirement for an optical modulator having both sufficient dynamic range and sufficiently wide bandwidth for directly transmitting ultrasound signals to the host electronics.